wiki.techinc.nl/includes/libs/objectcache/ReplicatedBagOStuff.php
Aaron Schulz dd97395104 objectcache: make BagOStuff::lock/unlock easier to override
Avoid the duplication of the reentrant lock logic in subclasses.

Move "lock already expired" logic from getScopedLock() to unlock()
so that it applies more generally. Warn when unlock() is called on
a key that is not even locked as well.

Also:
* Rename lock() $expiry argument to $exptime for consistency
* Fix return types for serialize()/unserialize()

Bug: T274174
Change-Id: I211536e616cf7f1cc60181c378bbf9b35ffa40a4
2021-07-19 19:40:17 +00:00

341 lines
9.3 KiB
PHP

<?php
/**
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
* @ingroup Cache
*/
use Wikimedia\ObjectFactory;
/**
* A cache class that directs writes to one set of servers and reads to
* another. This assumes that the servers used for reads are setup to replica DB
* those that writes go to. This can easily be used with redis for example.
*
* In the WAN scenario (e.g. multi-datacenter case), this is useful when
* writes are rare or they usually take place in the primary datacenter.
*
* @ingroup Cache
* @since 1.26
*/
class ReplicatedBagOStuff extends BagOStuff {
/** @var BagOStuff */
private $writeStore;
/** @var BagOStuff */
private $readStore;
/** @var int Seconds to read from the master source for a key after writing to it */
private $consistencyWindow;
/** @var float[] Map of (key => UNIX timestamp) */
private $lastKeyWrites = [];
/** @var int Max expected delay (in seconds) for writes to reach replicas */
private const MAX_WRITE_DELAY = 5;
/**
* Constructor. Parameters are:
* - writeFactory: ObjectFactory::getObjectFromSpec array yielding BagOStuff.
* This object will be used for writes (e.g. the primary DB).
* - readFactory: ObjectFactory::getObjectFromSpec array yielding BagOStuff.
* This object will be used for reads (e.g. a replica DB).
* - sessionConsistencyWindow: Seconds to read from the master source for a key
* after writing to it. [Default: ReplicatedBagOStuff::MAX_WRITE_DELAY]
*
* @param array $params
* @throws InvalidArgumentException
*/
public function __construct( $params ) {
parent::__construct( $params );
if ( !isset( $params['writeFactory'] ) ) {
throw new InvalidArgumentException(
__METHOD__ . ': the "writeFactory" parameter is required' );
} elseif ( !isset( $params['readFactory'] ) ) {
throw new InvalidArgumentException(
__METHOD__ . ': the "readFactory" parameter is required' );
}
$this->consistencyWindow = $params['sessionConsistencyWindow'] ?? self::MAX_WRITE_DELAY;
$this->writeStore = ( $params['writeFactory'] instanceof BagOStuff )
? $params['writeFactory']
: ObjectFactory::getObjectFromSpec( $params['writeFactory'] );
$this->readStore = ( $params['readFactory'] instanceof BagOStuff )
? $params['readFactory']
: ObjectFactory::getObjectFromSpec( $params['readFactory'] );
$this->attrMap = $this->mergeFlagMaps( [ $this->readStore, $this->writeStore ] );
}
public function get( $key, $flags = 0 ) {
$store = (
$this->hadRecentSessionWrite( [ $key ] ) ||
$this->fieldHasFlags( $flags, self::READ_LATEST )
)
// Try to maintain session consistency and respect READ_LATEST
? $this->writeStore
// Otherwise, just use the default "read" store
: $this->readStore;
return $store->proxyCall( __FUNCTION__, self::ARG0_KEY, self::RES_NONKEY, func_get_args() );
}
public function set( $key, $value, $exptime = 0, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function delete( $key, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function add( $key, $value, $exptime = 0, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function lock( $key, $timeout = 6, $exptime = 6, $rclass = '' ) {
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function unlock( $key ) {
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function deleteObjectsExpiringBefore(
$timestamp,
callable $progress = null,
$limit = INF,
string $tag = null
) {
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_NONKEY,
self::RES_NONKEY,
func_get_args()
);
}
public function getMulti( array $keys, $flags = 0 ) {
$store = (
$this->hadRecentSessionWrite( $keys ) ||
$this->fieldHasFlags( $flags, self::READ_LATEST )
)
// Try to maintain session consistency and respect READ_LATEST
? $this->writeStore
// Otherwise, just use the default "read" store
: $this->readStore;
return $store->proxyCall( __FUNCTION__, self::ARG0_KEYARR, self::RES_KEYMAP, func_get_args() );
}
public function setMulti( array $valueByKey, $exptime = 0, $flags = 0 ) {
$this->remarkRecentSessionWrite( array_keys( $valueByKey ) );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEYMAP,
self::RES_KEYMAP,
func_get_args()
);
}
public function deleteMulti( array $keys, $flags = 0 ) {
$this->remarkRecentSessionWrite( $keys );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEYARR,
self::RES_NONKEY,
func_get_args()
);
}
public function changeTTLMulti( array $keys, $exptime, $flags = 0 ) {
$this->remarkRecentSessionWrite( $keys );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEYARR,
self::RES_NONKEY,
func_get_args()
);
}
public function incr( $key, $value = 1, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function decr( $key, $value = 1, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function incrWithInit( $key, $exptime, $value = 1, $init = null, $flags = 0 ) {
$this->remarkRecentSessionWrite( [ $key ] );
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEY,
self::RES_NONKEY,
func_get_args()
);
}
public function getLastError() {
return ( $this->writeStore->getLastError() !== self::ERR_NONE )
? $this->writeStore->getLastError()
: $this->readStore->getLastError();
}
public function clearLastError() {
$this->writeStore->clearLastError();
$this->readStore->clearLastError();
}
public function makeKeyInternal( $keyspace, $components ) {
return $this->genericKeyFromComponents( $keyspace, ...$components );
}
public function makeKey( $collection, ...$components ) {
return $this->genericKeyFromComponents( $this->keyspace, $collection, ...$components );
}
public function makeGlobalKey( $collection, ...$components ) {
return $this->genericKeyFromComponents( self::GLOBAL_KEYSPACE, $collection, ...$components );
}
protected function convertGenericKey( $key ) {
return $key; // short-circuit; already uses "generic" keys
}
public function addBusyCallback( callable $workCallback ) {
return $this->writeStore->addBusyCallback( $workCallback );
}
public function setNewPreparedValues( array $valueByKey ) {
return $this->writeStore->proxyCall(
__FUNCTION__,
self::ARG0_KEYMAP,
self::RES_NONKEY,
func_get_args()
);
}
public function setMockTime( &$time ) {
parent::setMockTime( $time );
$this->writeStore->setMockTime( $time );
$this->readStore->setMockTime( $time );
}
/**
* @param string[] $keys
* @return bool
*/
private function hadRecentSessionWrite( array $keys ) {
$now = $this->getCurrentTime();
foreach ( $keys as $key ) {
$ts = $this->lastKeyWrites[$key] ?? 0;
if ( $ts && ( $now - $ts ) <= $this->consistencyWindow ) {
return true;
}
}
return false;
}
/**
* @param string[] $keys
*/
private function remarkRecentSessionWrite( array $keys ) {
$now = $this->getCurrentTime();
foreach ( $keys as $key ) {
unset( $this->lastKeyWrites[$key] ); // move to the end
$this->lastKeyWrites[$key] = $now;
}
// Prune out the map if the first key is obsolete
if ( ( $now - reset( $this->lastKeyWrites ) ) > $this->consistencyWindow ) {
$this->lastKeyWrites = array_filter(
$this->lastKeyWrites,
function ( $timestamp ) use ( $now ) {
return ( ( $now - $timestamp ) <= $this->consistencyWindow );
}
);
}
}
}